Earthworking machines, for example, wheel loaders, track loaders, and the like, having work implements, such as buckets, are often used to dig material from one location, and dump the material at one or more other locations. For example, wheel loaders having buckets are used to dig materials such as gravel, sand, soil, and the like, and dump the material into the bed of a truck, or at other sites.
In a work environment in which the dig and dump process is performed repeatedly for long periods of time, it is desired to work as efficiently and productively as possible. However, as fatigue sets in, or if the operator is relatively inexperienced, the dig cycle may not be as productive as desired. Furthermore, some work environments may be harsh for human operators, due to such factors as dust, weather, and adverse surroundings.
As a result, attempts have been made to automate the dig process to maximize productivity and efficiency. For example, in commonly-owned U.S. Pat. No. 5,968,103, Rocke discloses a system and method which automates the loading process of a work machine, such as a wheel loader, by monitoring various crowd factors as the bucket of the machine enters a pile of material. During the initial phase of the process, the system determines that the bucket has entered the pile, and responsively begins to lift the bucket rapidly. The lifting action of the bucket causes the front end of the work machine to be pushed downward, thus maintaining traction with the ground as the machine continues to push into the pile. The system then tilts the bucket back as it continues lifting in a controlled manner, thus loading the bucket to capacity.
The system disclosed by Rocke is designed to work with the engine of the work machine at full throttle. However, there are situations where it is desired to push into a pile of material with the engine at some speed less than full throttle. For example, the ground may be wet or sandy, and thus not able to provide good traction. Maintaining the engine at full speed may then cause the work machine to slip excessively as it enters the pile.
When the engine is operated at less than full speed, however, the invention disclosed and claimed by Rocke continues to command the same lift velocity as before. This results in the bucket rising out of the pile too quickly, thus causing the automated dig cycle to no longer load the bucket to capacity. It is desired therefore, to improve the invention disclosed by Rocke to adjust the automated bucket loading cycle to compensate for variations in engine speed.
The present invention is directed to overcoming one or more of the problems as set forth above.